Process for the production of magnesium-zirconium alloys



Patented Jan. 14, 1941 PROCESS FOR THE PRODUCTION OF MAG- NESIUM-ZIRCONIUM ALLOYS Franz Sauerwalil, Breslau, Germany. asslgnor, by

mesne assignments, to

Magnesium Development Corporation, a corporation of Delaware No Drawing.

Application October 28, 1939, Se-

rial No. 301,827. In Germany November 8,

Claims.

This invention relates to a process for the,

production of magnesium-zirconium alloys.

In the production of magnesium alloys containing zirconium, whether by the direct introduction of metallic zirconium into molten magnesium or by the reduction of salts of zirconium, it has hitherto been found impossible, even when employing the measures usually adopted for the in--= corporation of metals difilcult to alloy with magnesium, to increase the zirconium content in the magnesium beyond about 2 per cent., even when the temperature of the melt has been raised to near the boiling point of magnesium.

Since, on the other hand, hitherto unpublished experiments have shown that, in the solid state, the solubility of zirconium in magnesium increases with the temperature, attempts were made to obtain true alloys of magnesium having higher contents of zirconium, by diifusion in the solid condition. With this object, plates of pure magnesium were embedded in zirconium powder and treated, for protracted periods at temperatures only slightly below the melting point of pure magnesium. In this manner alloys have been produced which contain up to about 4 per cent. ofv

zirconium in solid solution in the magnesium.

Such a cementation process is, however, obviously useless for the production of magnesiumzirconium alloys on a manufacturing scale.

The present invention provides a process of producing magnesium-zirconium alloys in the form of pieces of any convenient size and shape, which comprises preparing a suspension of elementary zirconium in molten magnesium, and

' transforming said suspension by rapid cooling,

into the solid state, so that the suspension of zirconium in the magnesium is still retained therein. Thereafter, the solidified suspension is subjected to prolonged heat treatment at high temperatures, such as 600 C., which completes the diffusion of the zirconium suspended in the magnesium, with formation of a true alloy.

The same efiect is obtained by stirring zirconiumpowder into the molten magnesium, or

' magnesium alloy, and thereafter cooling the mixture to a temperature slightly exceeding the solidus point, and stirring the crystalline pulp energetically, for a considerable time, at that temperature. The mixture is finally cooled until completely solidified, and is then preferably again annealed, for some little time, at a temperature closely below the solidus point.

The suspension of elementary zirconium in molten magnesium can also be prepared by stirring metallic zirconium, in an extremely fine state of division, into the molten magnesium and also by the intrcduction, into the molten magnesium, of zirconium salts which are then reduced to the metallic state.

The process is also specially adapted for the production of pre-alloys of magnesium and zirconium which are high in the latter component.

Example 1.15 kgs. of pure magnesium are fused, after which 1.2 kgs. of zirconium powder are stirred into the melt at a temperature of about 700 C. The stirring of the suspension thus formed ing it into iron moulds, in which it undergoes rapid quenching. The cast ingots are afterwards placed in an annealing furnace and maintained therein at a temperature of 620 C. for 112 hours. The alloy treated in this manner contains 3.68 per cent. of zirconium in solution.

Example 2.Into 15 kgs. of pure molten magnesium are stirred 1.5 kgs. zirconium powder, and

the suspension thus formed is cooled down to a temperature of 650 C. the stirring of the crystalline pulp being continued, at that temperature, for 2 hours, and followed by cooling to a temperature of 645 C., at which the alloy solidifies completely. The annealing is continued at said temperature for 4 days, the alloy then containing 4.52 per cent. of zirconium in solution, whilst 4.33 per cent. remains undissolved.

What I claim is: p

1. A process for the production of magnesium zirconium alloys which comprises producing a dispersion of unalloyed solid zirconium in magnesium and subjecting the solidified product for an extended period of time to temperatures adapted to cause diffusion of the dispersed zirconium in the magnesium matrix.

2. A process for the production of magnesiumzirconium alloys which comprises producing a dispersion of unalloyed solid zirconium inmolten magnesium, rapidly solidifying the mixture, and

subjecting the solidified mixture to temperatures below the melting point of magnesium for a period of time sufficient to cause difiusion of the dispersed zirconium in the solid magnesium matrix.

3. A process for the production of magnesiumzirconium alloys which comprises producing a dispersion of unalloyed solid zirconium in molten magnesium, rapidly solidifying the mixture and subjecting the solidified mixture to temperatures of the order of 600 C. for a period of time sufiicient to cause diflusion of the dispersed zirconium in the solid magnesium matrix.

is continued up to the time of pour- 4. A process for the production of magnesium 66 zirconium alloys which comprises producing a dispersion of unalioyed solid zirconium in molten magnesium, withdrawing heat from the mixture so as to cause partial crystallization of the magnesium while energetically stirring the crystalline pulp thus produced for a period of time sufficient to cause diffusion of dispersed zirconium in the solid magnesium matrix, and subsequently cooling the product to a temperature below the point of complete solidification.

5. A process for the production of magnesiumzirconium alloys which comprises producing a dispersion of unalloyed solid zirconium in molten magnesium, withdrawing heat from the mixture so as to cause partial crystallization of the magnesium while energetically stirring the crystalline pulp thus produced for a period of time suflicient to cause diffusion of dispersed zirconium in the solid magnesium matrix, subsequently cooling the product to a temperature below the point 01 complete solidification, and finally subjecting the product to a prolonged heating within such last- 10 named temperature range.

FRANZ SAUERWALD. 

